init

.gitignore

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+/target

Cargo.toml

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+[package]
+name = "egui_qr"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+egui = { version = "^0.20", default-features = false }
+qrcode = { version = "0.14.1", default-features = false }
+
+[dev-dependencies]
+eframe = "^0.20"

examples/main.rs

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+use eframe::{Frame, NativeOptions};
+use egui::{CentralPanel, Context, Widget};
+use egui_qr::QrCodeWidget;
+use qrcode::QrCode;
+
+fn main() {
+    let _ = eframe::run_native(
+        "egui_qr",
+        NativeOptions::default(),
+        Box::new(|_| Box::new(App)),
+    );
+}
+
+struct App;
+
+impl eframe::App for App {
+    fn update(&mut self, ctx: &Context, frame: &mut Frame) {
+        let code = QrCode::new(b"hello").unwrap();
+        CentralPanel::default().show(ctx, |ui| {
+            QrCodeWidget::new(&code).ui(ui);
+        });
+    }
+}

src/lib.rs

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+use egui::{vec2, Color32, Rect, Response, Rounding, Sense, Stroke, Ui, Widget};
+use qrcode::{Color, QrCode};
+
+pub struct QrCodeWidget<'a> {
+    code: &'a QrCode,
+}
+
+impl<'a> QrCodeWidget<'a> {
+    pub fn new(code: &'a QrCode) -> Self {
+        QrCodeWidget { code }
+    }
+}
+
+impl Widget for QrCodeWidget<'_> {
+    fn ui(self, ui: &mut Ui) -> Response {
+        let size = ui.available_size();
+
+        let (response, painter) = ui.allocate_painter(size, Sense::click());
+        let w = self.code.width();
+        let start = response.rect.min;
+        let mut ctr = 0;
+        let scale = (size.x / w as f32).floor();
+        for c in self.code.to_colors() {
+            let row = ctr / w;
+            let col = ctr % w;
+            let c_start = start + vec2(col as f32 * scale, row as f32 * scale);
+            let c_end = c_start + vec2(scale, scale);
+            painter.rect(
+                Rect::from_min_max(c_start, c_end),
+                Rounding::none(),
+                match c {
+                    Color::Light => Color32::WHITE,
+                    Color::Dark => Color32::BLACK,
+                },
+                Stroke::NONE,
+            );
+            ctr += 1;
+        }
+        response
+    }
+}